1. Enhanced Beacon Sync Frame for the 802.22.1
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Enhanced Beacon Sync Frame for the
IEEE P Wireless RANs Date:
Authors:
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Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

2. Jan 2007
doc.: IEEE /0xxxr0
January 2007
Abstract
An enhanced Beacon Sync Frame scheme for IEEE Std is proposed. This new scheme will provide error correction and error detection capability for the Sync Frame. Compared to the previous proposal in [1], the number of parity bits was reduced and PSDU type information was added so that the WRAN can decide whether it should schedule Quiet Period to listen to the PSDU or not in advance.
We also suggest a sensing method by which, with a ms sensing window, the WRAN can sense beacons without affecting its communication.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

3. Content Enhanced Sync Frame Scheme Proposed Encoding and Decoding
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Content
Enhanced Sync Frame Scheme Proposed
Encoding and Decoding
Simulation Results
Beacon Sensing method of WRAN
Conclusions
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

4. Enhanced Sync Frame Scheme Proposed (1/2)
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Enhanced Sync Frame Scheme Proposed (1/2)
Sync Frame
With Index X
X-1
。。。
PSDU Frame
Sync Sequence
(15 bits)
PSDU Type
(1 bit)
Index
(6 bits)
Parity
(8 bits)
Sync Frame Structure
Super Frame Structure
DTX(2
bits)
Figure 1: The Enhanced Beacon Sync Frame structure
The Enhanced Beacon Sync Frame has now 32 bits in total, including 15-bit PN Sequence, 15-bit Information (consisting of 1-bit PSDU type information which tell the following PSDU is for WRAN or for beacon-to-beacon communication, 6-bit Index and 8-bit Parity) and 2-bit DTX (Discontinuous Transmission).
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

5. Enhanced Sync Frame Scheme Proposed (2/2)
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Enhanced Sync Frame Scheme Proposed (2/2)
Within the Sync Frame, the PSDU type and Index part need to be decoded successfully with high reliability. Otherwise, the receiver can’t decode the PSDU correctly. So we apply FEC (15, 7) to provide Error Correction and Error Detection capability on the PSDU type and Index part. Also, for the alignment reason, the Sync Frame should include integral number of bytes. So we add 2 DTX bits at the end of a Sync Frame to make it 32bits or 4 bytes in total. Later, we will see that these 2 DTX bits are also helpful to detect the PN Sequence with a small sensing window size.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

6. Encoding and Decoding (1/4)
January 2007
Encoding and Decoding (1/4)
The FEC code we select here is a code, which is a (n,k) = (15, 7) linear block code.
In the transmitter side, the encoding is just like adding a CRC. The generator polynomial we are using here is
The 1-bit PSDU Type and 6-bit Index are combined together as a message to be encoded and denoted in a polynomial form as
Wu Yu-Chun, Huawei Hisi

7. Encoding and Decoding (2/4)
January 2007
Encoding and Decoding (2/4)
Then The data will be transmitted in the order of where is transmitted first.
Wu Yu-Chun, Huawei Hisi

8. Encoding and Decoding (3/4) Figure 2: The Encoding Circuit of FEC
January 2007
Encoding and Decoding (3/4)
The Encoding procedure can be implemented as in the following diagram:
Figure 2: The Encoding Circuit of FEC
Wu Yu-Chun, Huawei Hisi

9. Encoding and Decoding (4/4) Figure 3: The Decoding Circuit of FEC
January 2007
Encoding and Decoding (4/4)
The decoder can be implemented as in the following circuit diagram: …
Figure 3: The Decoding Circuit of FEC
Wu Yu-Chun, Huawei Hisi

10. Simulation Results (1/2)
January 2007
Simulation Results (1/2)
The simulation results of 7-bit message without FEC and 15-bit with FEC(15,7) on the AWGN channel are plotted in the following figure.
Figure 4: Simulation Results of Sync Frame
Wu Yu-Chun, Huawei Hisi

11. Simulation Results (2/2)
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Simulation Results (2/2)
From the simulation results, we can see that the gain of the FEC(15,7) over that without FEC is about 4.5dB in SNR sense and 1.5dB in Eb/N0 sense.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

12. Beacon Sensing method of WRAN (1/5)
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Beacon Sensing method of WRAN (1/5)
As analyzed in [2], a small sensing window is very important for the WRAN not to affect its communication while sensing. To make the sensing window as small as possible, we propose the use of QPSK modulation. Then the time duration of one Sync Frame is ms (corresponding to 32 bits or 16 QPSK symbols). The time duration of the PN sequence is ms, which is half of the total Sync Frame.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

13. Beacon Sensing method of WRAN (2/5)
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Beacon Sensing method of WRAN (2/5)
Here we introduce a sensing method based on two properties of the Sync Frame:
Good correlation property of the Fixed PN Sequence.
The 2 bits of DTX (1 QPSK symbol) at the end of each Sync Frame notifies that the Beacon stops its transmission.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

14. Beacon Senseing method of WRAN (3/5)
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Beacon Senseing method of WRAN (3/5)
As illustrated in Figures 5 and 6 in the following slide, suppose we have saved 16 QPSK symbols. Then the sensing procedure is as following:
1) Find the DTX symbol. This can be done in a very simple way by finding a symbol position with the lowest energy.
Rearrange the saved data properly as illustrated in Figures 5 and 6 to get a continuous and complete PN Sequence.
Calculate the correlation value of the PN Sequence.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

15. Beacon Senseing method of WRAN (4/5)
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Beacon Senseing method of WRAN (4/5)
Judge whether there is a beacon signal or not: if the lowest energy detected meets a certain criterion (for example, the lowest energy is below 1/5 of the average energy) and the correlation value meets with another criterion (for example, the auto-correlation value is more than 5 times of cross-correlation value), then we judge that there is a Beacon Sync Frame. Otherwise, there is not.
If, after Step4, the WRAN judges there is a beacon and knows the start position of the Sync Frame, it can decode the Sync Frame to get the PSDU type and Index information in the next shot.
After getting PSDU type and Index information, the WRAN can decide whether to schedule proper Quiet Period to listen to the PSDU of that beacon.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

16. Beacon Senseing method of WRAN (5/5)
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Beacon Senseing method of WRAN (5/5) PN D
Saved Data
Information
(a) Original received data
(b) Data after rearrangement
Rearranged data
Figure 5: The data WRAN saved starts in the PN part PN D
Saved Data
Information
(a) Original received data
Figure 6: The data WRAN saved starts in the Information part
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

17. Comparison of Series and parallel transmission of Beacon Sync and PSDU
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Comparison of Series and parallel transmission of Beacon Sync and PSDU I
Sync Frame
Sync Frame
。。。
Sync Frame Q
PSDU
Figure 6a: Parallel transmission of Beacon Sync and PSDU
Pro: Can receive Sync Frame at any time
Con: need longer time to receive one Sync Frame I
Sync
Frame
Sync
Frame
。。。
Sync
Frame
PSDU Q
Figure 6b: Series transmission of Beacon Sync and PSDU
Pro: need shorter time to receive one Sync Frame
Con: Can’t receive the Sync Frame at any time
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

18. Jan 2007
doc.: IEEE /0xxxr0
January 2007
Conclusions (1/2)
From the previous slides, we can see that the Enhanced Sync Frame Scheme has following advantages:
The Enhanced scheme provides error correction capability, which greatly improves the Sync performance (about 4.5dB in SNR sense and 1.5dB in Eb/N0 sense).
The FEC also provides error detection capability. This is very important to ensure that the WRAN does not waste a long Quiet Period to decode the PSDU when it did not get the correct start position of the PSDU.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

19. Jan 2007
doc.: IEEE /0xxxr0
January 2007
Conclusions (2/2)
The FEC used here has a very simple encoding algorithm as well as a very simple decoding algorithm. The encoding procedure is just like adding a CRC. Regarding decoding complexity, only three XOR operations, one addition operation, and one comparison operation are needed for each bit.
We also introduce a sensing method by which with the sensing window size of ms, the WRAN can sense beacons without interruption of its communications .
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

20. Jan 2007
doc.: IEEE /0xxxr0
January 2007
References
《 _Huawei_Beacon_Sync_Frame_Proposal》.
《 _WRAN_Sensing_Window》
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

21. Any comments and questions will be highly appreciated!
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Thank you!
Any comments and questions
will be highly appreciated!
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi